The fossils were found in the Rhynie Chert, a formation where silica-laden water bubbled up from volcanic hot springs, instantly petrifying lichen, plants and primitive insects in stunning detail. [Video: See The Ancient Arachnid's Creepy Walk]

The team used several specimens of the extinct spider ancestor, named Paleocharinus, which were housed in the Natural History Museum in London. When the extinct spider ancestor crawled about Earth during the Devonian Period — between 416 million and 358 million years ago — most life still lived in the oceans, though the first insects, including Paleocharinus, first emerged on land.

The new simulation suggests that the creature moved much like modern cursorial spiders, which walk throughout the day to chase prey and run to evade predators. Paleocharinus may have been an ambush predator, sneaking up on prey and pouncing, the researchers write in a paper published in Tuesday's issue of the Journal of Paleontology.

"Long before our ancestors came out of the sea, these early arachnids were top dog of the food chain," study co-author Russell Garwood, a paleontologist in the University of Manchester, said in a statement.

During its heyday, the arachnid was more widespread than spiders are today, Garwood said. But the loss of swampy forests, predation by four-legged creatures, and the rise of spiders may have doomed these creatures to extinction.